CodeGrinder is a tool that hosts programming exercises for students. Problems are graded using unit tests, and scores are posted back to an LMS such as Canvas using the LTI protocol.

This is a tool we use internally at Utah Tech University in our Computer Science program. It is pretty stable and we have been using it for years, but it is mostly an internal project. I recommend getting in touch if you would like to use it.

CodeGrinder is released under the terms of the AGPL. If you would like to use it and these terms are not suitable, please contact the author to inquire about alternate licensing.

This repository currently hosts three tools:

1. The CodeGrinder server. This is further divided into two parts, which can run as part of the same service, or can be hosted on separate servers. A CodeGrinder installation needs exactly one TA service and one or more daycare services.

   1. The TA service: this manages bookkeeping and runs on top of SQLite 3. It interfaces with an LMS by acting as an LTI tool provider. An LMS such as Canvas hosts an assignment page, and directs students to the TA service complete with basic credentials, login information, and information about the problem set that was assigned. The TA then acts as an API server for basic bookkeeping tasks.

   2. The daycare service: this runs student code with problem-specific unit tests in Docker containers, streams the results back to the client in real time, and returns a report card with the results.

2. The grind command-line tool. This provides a command-line user intereface for students, instructors, and problem authors. Students can see their currently-assigned problems, pull them onto their local machines, and submit them for grading.

3. The Thonny plugin. This adds a CodeGrinder menu to Thonny for Python problems. Students can log in and out, download new assignments, test their code locally, and submit it for grading.

All instructions here assume a Debian Bookworm or Ubuntu Server 22.04 server environment.

Install a few basic tools:

sudo apt install build-essential golang git sqlite3

The host must have port 443 open to serve the API over https, and it must also have port 80 open so LetsEncrypt can issue certificates.

Fetch the CodeGrinder repository:

cd
git clone https://github.com/russross/codegrinder.git
cd codegrinder

The rest of these instructions assume you are in the project root directory.

Build and install CodeGrinder. For a TA node, use:

./all.sh

This builds codegrinder (the server) and installs it in /usr/local/bin. It also builds the grind tool for several architectures and puts them in the www directory for users to download.

For a daycare node that is not also a TA node, use:

./build.sh

This only builds and installs the server. Both of these scripts also give the codegrinder binary the capability to bind to low-numbered ports, so CodeGrinder does not need any other special privileges to run. It should NOT be run as root.

Run the database setup script. Warning: this will delete an existing installation, so use this with caution.

./setup/setup-database.sh

Install and configure Docker, and add your CodeGrinder user to the docker group so it can manage containers without being root. Note that you only need this on daycare nodes:

sudo apt install docker.io
sudo usermod -aG docker $USER

Next, create a config file that is customized for your installation. It should be saved as ~/codegrinder/config.json and its contents depend on what role this node will take. All nodes should contain the following:

{
    "hostname": "your.domain.name",
    "daycareSecret": "",
}

Put in your domain name to use when registering TLS certificates with LetsEncrypt.

For the node running the TA role, you should add these keys:

    "ltiSecret": "",
    "sessionSecret": "",

and for nodes running the daycare role, you should add these keys:

    "taHostname": "your.ta.domain.name",
    "capacity": 1,
    "problemTypes": [
        "python3unittest"
    ],

making sure to list all of the problem types this daycare will process.

Note that this is a JSON file, so every entry should have a trailing comma except for the last one, which must not end with a comma.

For the secrets, generate each one using:

head -c 32 /dev/urandom | base64

Run that command once and copy the output into the ltiSecret, then run it again and copy the output to sessionSecret, then run it a third time and copy the output to daycareSecret. The daycareSecret value must be shared by all nodes.

Note that there are other settings available that allow you to customize the installation, but they are not documented here. If you need them, check out the Config type defined in codegrinder/server.go. The fields of that struct are the fields of the config file.

For daycare nodes, you must also build the Docker images that will host the student code:

make -C ./containers amd64

Or if you are running on a Raspberry Pi and need the ARM64 images:

make -C ./containers arm64

At this point, you should be able to run the server. To run it with only the TA service, use:

codegrinder -ta

If you want a daycare running on the same node, use:

codegrinder -ta -daycare

Leave it running in a terminal so you can watch the log output.

For normal use, you will want systemd to manage it:

sudo cp ./setup/codegrinder.service /lib/systemd/system/

Then edit the file you have copied to customize it. In particular, set the options in the executable to run as -ta, -daycare, or both, and in the dependencies section comment out the docker dependency if this is not a daycare node.

To start it, use:

sudo systemctl start codegrinder

To set it to automatically start at system boot:

sudo systemctl enable codegrinder

To stop it:

sudo systemctl stop codegrinder

To check if it is running and see the most recent log messages:

sudo systemctl status codegrinder

To review the logs:

sudo journalctl -xeu codegrinder

To follow the logs in real time:

sudo journalctl -xfu codegrinder

There is also a script in the setup directory to take daily backups of the database. It will keep seven days worth of backups, along with four weekly backups, twelve monthly backups, and a backup at the end of each semester. Set the script to run daily using cron:

crontab -e

Then add a line like this to the end of the file:

7 5 * * * /home/russ/codegrinder/setup/backup-codegrinder-database

with the directory set to match your installation location. This will create a snapshots of the database in ~/codegrinder/backup. I have a cron job on a different machine run a little while after the backup that uses rsync to clone the backup directory on that other machine.

CodeGrinder is licenced under the AGPL. I am willing to consider re-licensing CodeGrinder under a more permissive license, depending on the use case. Please contact me if you wish to discuss this.

CodeGrinder programming exercise system Copyright © 2016–2024 Russ Ross

This program is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more details.

You should have received a copy of the GNU Affero General Public License along with this program. If not, see http://www.gnu.org/licenses/.